Germanium crystals



Patented Aug. 21, 1951 GERMANIUM CRYSTALS Salvatore F. Amico, EastBoston, Mass., assignor to Sylvania Electric Products Inc., Salem,Mass., a corporation of Massachusetts No Drawing.

3 Claims.

This invention relates to semi-conductors such as germanium crystals,andparticularly to the preparation of such crystals.

I find that the addition of a small amount of germanium dioxide to thegermanium metal permits the use of a less pure germanium startingmaterial, and thereby greatly reduces the cost of manufacturing, whileimproving the electrical characteristics of the resultant crystal.

Other objects, features and advantages of the invention will be apparentfrom the following specification. 1

In making a germanium crystal suitable for rectification, oscillation,amplification and the like I may take germanium dioxide in the form of afine white powder and reduce it in an atmosphere of hydrogen at atemperature of about 700 C. for several hours, for example, three hoursto give a fine black powdered germanium metal. This may be placed in aquartz crucible, together with about 1% of metallic tin in the form ofparticles which may for example be such as would pass through athirty-mesh screen. About 0.1% germanium dioxide in finely powdered formis added to these components, and made into a homogeneous mixturetherewith, for example, by rolling them together on a sheet of paper.The germanium dioxide should be less than about 0.2%, about 0.1% givingthe best results. The amount of tin may be varied, for example, fromabout 0.2% to about 4%, but 1% is the preferable proportion;

The powdered mixture of germanium, tin and germanium dioxide, is heatedto about 1000" C. and cooled slowly to the freezing point of theresultant melt. About fifty minutes may be allowed to elapse while themelt is being cooled from 1000 C. to its freezing point, and thetemperature may be held at the freezing point for about ten minutesafter which the heat may be removed and the material allowed to cool toroom temperature in the absence of any heat Application July 16, 1948,Serial No. 39,199

2 now abandoned, or as in a co-pending application of et Casellini,Serial 492,163, filed June 23, 1943, for Electrical Rectifiers, or insome other convenient manner.

supplied to the material. The crystal may then be used in a device forexample, as shown in my co-pending application Serial 749,471, filed Theexact function of the germanium dioxide in the melt is not'definitelyknown, but its use permits manufacture from inferior and somewhat impuregermanium materials of crystals with extremely good electricalcharacteristics for rectification, oscillation, amplification and thelike.

The addition of some activating impurity such as tin is generallynecessary to make good germanium crystals for use as semiconductors:however, other materials than tin may be used.-

What I claim is:

1. The method of making semi-conductive germanium including the step ofmelting purified pulverulent germanium together with about 0.1% ofpulverulent germanium dioxide in contact with an activating impurity.

2. A semiconductive ingot made by melting purified pulverulent germaniumtogether with about 0.1% of pulverulent germanium dioxide in contactwith an activating impurity.

3. The method of making semiconductive germanium, including the steps ofmixing together purified pulverulent germanium together with about .192,of pulverulent germanium dioxide and .2% in 4% tin, melting thismixture, and slowly allowing the mixture to cool.

SALVATORE F. AMIGO.

REFERENCES CITED The following references are of record in the file ofthis patent:

3. THE METHOD OF MAKING SEMICONDUCTIVE GERMANIUM, INCLUDING THE STEPS OFMIXING TOGETHER PURIFIED PULVERULENT GERMANIUM TOGETHER WITH ABOUT .1%OF PULVERULENT GERMANIUM DIOXIDE AND .2% IN 4% TIN, MELTING THISMIXTURE, AND SLOWLY ALLOWING THE MIXTURE TO COOL.